A haying machine normally has a frame carried on the three-point hitch of a tractor. During use of the haying machine the frame is lowered down so that the machine can ride via a plurality of castering wheels on the ground. Each of these wheels is associated with a respective set of spring tines that serves to turn or ted hay lying on the ground underneath the machine, as described in German patent document No. 2,156,229 of G. Knusting.
It is normally considered necessary to be able to vary the vertical height of the spring tines carried by the wheel relative to the ground. This is most easily done by providing some adjustment means for displacing the wheel relative to the mechanism carrying the spring tines. Austrian Pat. No. 198,559 and U.S. Pat. No. 2,194,617 describe a system wherein the wheel is carried on a spindle slidable in a support and formed with a row of laterally open holes. A pin can engage from the support into the holes to allow the spindle carrying the wheel to be set at heights corresponding to the levels of the holes.
This system, which is typical of the adjustment systems used in the wheel assemblies of haying machines, provides only a relatively coarse adjustment of the wheel height. Furthermore the system has the disadvantage that the wheels frequently position themselves backward or perpendicular to the travel direction, so that when the haying machine is lowered down into contact with the ground quite some force must be exerted on them to spin them around, this force at least temporarily distorting the frame of the haying machine.